Severity of spinal cord dysfunction and pain associated with hydrated nucleus pulposus extrusion in dogs

Prevalence of neurological diseases associated with cervical pain and/or signs of cervical myelopathy in French bulldogs: a retrospective analysis of 105 cases

Introduction

French bulldogs can be affected by several neurological diseases, with myelopathies representing the most frequent cause of neurological signs. Studies focusing on the epidemiology of cervical diseases in this breed are lacking. This study aims to describe the prevalence of neurological pathologies responsible for cervical pain and/or signs of cervical myelopathy, assuming that intervertebral disc herniation represents the most common disease; a second aim was to evaluate how often different pathologies coexist in this spinal region in French bulldogs.

Materials and methods

A retrospective analysis of medical records from the database of a single referral center (AniCura I Portoni Rossi Veterinary Hospital-Zola Predosa, Bologna, Italy) was performed, including French bulldogs presented for neck pain and/or neurological deficits consistent with cervical myelopathy. Clinical and imaging data were reviewed and used as inclusion criteria. Based on the number of MRI-diagnosed diseases, the eligible dogs were divided into three groups.

Results

One hundred five French bulldogs met the inclusion criteria. The most commonly diagnosed condition was an intervertebral disc herniation (66.9%), followed by C2 idiopathic hypertrophic ganglioneuritis (15.1%), cervical syringomyelia (11.5%), congenital osseous malformations (1.4%), spinal arachnoid diverticula (1.4%), neoplasms (1.4%), steroid-responsive meningitis-arteritis (0.7%), traumatic vertebral fractures (0.7%), and other (0.7%). For the vast majority of dogs (75/105) a single pathology was diagnosed, with intervertebral disc herniations accounting for 86.7% of cases, involving C3-C4 IVD most commonly. In the remaining 30 dogs, two or three different and concurrent diseases were detected. Among these 30 dogs, intervertebral disc herniations still remained the most diagnosed condition, in combination with C2 idiopathic hypertrophic ganglioneuritis and syringomyelia in 19 and seven cases, respectively.

Conclusion

The results of this study highlight that different pathologies can affect the cervical spinal cord in French bulldogs, with intervertebral disc herniations representing the most frequent condition, as previously described in the veterinary literature. In almost a third of cases, different pathologies can coexist at the cervical level. However, for cases in which different pathologies are present at the same time, it is not always possible to clearly establish their clinical significance.

Thoracolumbar hydrated nucleus pulposus extrusion and intervertebral disc extrusion in dogs: Comparison of clinical presentation and magnetic resonance imaging findings

Thoracolumbar hydrated nucleus pulposus extrusion (TL-HNPE) is an increasingly recognised pathology with a substantial lack of literature describing its features. The aim of this retrospective case-control study was to analyse the clinical and magnetic resonance imaging (MRI) features of dogs with TL-HNPE compared to dogs affected with thoracolumbar intervertebral disc extrusion (TL-IVDE). Data from dogs diagnosed with TL-HNPE and TL-IVDE via MRI at two referral hospitals, were retrospectively collected and compared in terms of clinical signs and MRI features. Cases diagnosed with TL-IVDE were deemed controls. The MRI features of the affected IVD space, herniated IVD material, affected overlying spinal cord and local epaxial musculature were evaluated for each group. Fifty-one cases with TL-HNPE and 105 randomly selected cases of TL-IVDE were included. Several signalment and neurological signs were identified as statistically distinct between groups in univariate analysis. Multivariate analysis identified that dogs affected with TL-HNPE were typically older, less likely to be chondrodystrophic (62.2 % vs. 91 %), more frequently experiencing a peracute onset (90.2 % vs. 61.9 %) often attributed to a suspected trauma linked with exercise (37.3 % vs. 10.5 %), being less frequently progressive (41.2 % vs. 86.5 %) and with herniated disc material less frequently lateralised (72.6 % vs. 89.5 %) than cases with TL-IVDE. MRI-identifiable intervertebral disc degeneration was found in every TL-IVDE case but only in 60 % of TL-HNPE cases. TL-HNPEs were associated to significantly less spinal cord compression and less hyperalgesia than TL-IVDE.

Myelo-CT imaging findings in 15 dogs with surgically-treated cervical acute compressive hydrated nucleus pulposus extrusion

Compressive hydrated nucleus pulposus extrusion (HNPE) is a sudden extrusion of hydrated, nondegenerated nucleus pulposus material with well-known characteristic MRI findings. The appearance of compressive HNPE during contrast-enhanced CT has already been described, but never its myelo-CT characteristics. The aim of this retrospective multicenter case series is to describe the myelo-CT findings in 15 dogs with compressive HNPE confirmed with gross surgical findings. A distinctive and consistent myelo-CT appearance of cervical compressive HNPE in dogs that included a focal extradural "seagull"-shaped extradural compression dorsal to the annulus fibrosus combined with a narrowing of the affected intervertebral disc space was found. The extruded material was hypoattenuating in the soft tissue algorithm. Myelo-CT could be a useful diagnostic tool and influence the clinical decision to address cervical compressive HNPE conservatively or surgically when MRI is not available.

A 50‐step walking test for analysis of recovery after decompressive surgery for thoracolumbar disc herniation in dogs

Background

Despite its importance, there is no agreed definition of recovery of ambulation in dogs with spinal cord injury.

Objectives

To validate a new walking test in dogs recovering from thoracolumbar spinal cord injury.

Animals

Two hundred twenty‐four dogs weighing <20 kg: 120 normally ambulatory dogs, plus 104 dogs undergoing decompressive surgery for acute thoracolumbar intervertebral disc herniation.

Methods

Prospective cohort studies. The distance each freely‐ambulatory dog walked during 50 step cycles was regressed on ulna length. For each postsurgical dog, we recorded when the calculated 50‐step distance was completed without falling, or their inability to complete this distance by 4 months or more after surgery. Bayesian analysis compared outcomes for presurgical neurologic categories; association of recovery with several preoperative variables was explored using logistic and time‐to‐event regression.

Results

For control dogs, 50‐step distance (m) = 1.384 × ulnar length (cm) + 2.773. In postsurgical dogs, the 50‐step test provided decisive evidence that deep pain‐negative dogs were less likely to recover ambulation than dogs with intact pain perception (12/29 recovered vs 71/75; Bayes factor [BF] = 5.9 × 10⁶) and, if they did recover, it took much longer (median 91 days vs median 14 days; BF = 1.5 × 10³). Exploratory analysis suggested that presurgical neurologic status (subhazard ratio [SHR] = 0.022; P < .001) and duration of presurgical anesthesia (SHR = 0.740; P = .04) were associated with rapidity of recovery.

Conclusions and Clinical Importance

This straightforward 50‐step walking test provides robust data on ambulatory recovery well‐suited to large scale pragmatic trials on treatment of thoracolumbar spinal cord injury in dogs.

Hydrated Nucleus Pulposus Extrusion in Dogs: Thoracolumbar Compared to Cervical Cases

OBJECTIVE

 The aim of this study was to review and describe cases of thoracolumbar (TL) hydrated nucleus pulposus extrusion (HNPE) diagnosed with magnetic resonance imaging and surgery, and compare them to cases of cervical (C) HNPE.

STUDY DESIGN

 Retrospective, single-center study.

RESULTS

 Thirty-six dogs met the inclusion criteria. Fifteen cases were C and 21 TL. Thirteen dogs were chondrodystrophic breeds, mean body weight was 13 kg, median age was 7.5 years, and 30/36 were male. Fewer dogs were chondrodystrophic in the C group compared with the TL group (p = 0.022). More than 90% had an acute onset, and strong activity was more often reported in the TL group. TL HNPE was more often painful, and extruded disc material more often lateralized (p = 0.017). Median Modified Frankel Score at presentation was 3 and 72.2% were non-ambulatory. More TL HNPE (11/21) were treated surgically compared with C HNPE (4/15). Treatment choice was correlated with spinal cord compression (p = 0.0075). Median Modified Frankel Score improved during hospitalization (p = 0.002) and there was no difference in outcome between C and TL HNPE or conservative and surgical treatment. Mean follow-up time was 33 days. All patients were ambulatory at follow-up.

CONCLUSION

 This study suggests that the HNPE is not limited to the C vertebral column of dogs and can occur in the TL vertebral column as well. Dogs with TL HNPE show spinal hyperesthesia more often and extruded nucleus material is more often lateralized. Outcome is similar to what has previously been described for C HNPE.

Distraction Stabilization of Degenerative Lumbosacral Stenosis: Technique and Mid- to Long-Term Outcome in 30 Cases

OBJECTIVE

 To describe the dorsal laminectomy, annulectomy and distraction stabilization with pins and polymethylmethacrylate technique, its complications and outcome in the management of canine degenerative lumbosacral stenosis. To determine pre- and post-surgical foraminal width and vertebral step changes.

STUDY DESIGN

 Multi-institutional retrospective clinical study.

METHODS

 Medical records (2005-2020) of dogs treated (n = 30). Clinical signs, Modified Frankel Score, Texas Spinal Cord Injury Score, pain score (dorsal palpation of spine, tail dorsiflexion), imaging findings and complications were retrieved pre-operatively, perioperatively and at long-term follow-up.

RESULTS

 The most common presurgical imaging findings were disc protrusion (24/25) and sclerosis of the caudal end-plate of L7 (23/30). On short- to long-term assessment 18 out of 21 dogs exhibited clinical improvement and all exhibited improved pain scores (p < 0.0001). Catastrophic complications occurred in 3 dogs, and major complications occurred in 5, of which 3 required additional surgery. Mean lumbosacral step defect reduced 60% (1.8 mm ± 2.5 mm pre-surgery to 0.7mm ± 0.9mm post-surgery, p = 0.1585). Mean foraminal width significantly increased 50% long-term (3.3 mm ± 1.0 mm pre-surgery to 5.0 mm ± 0.9 mm post-surgery, p < 0.0001).

CLINICAL SIGNIFICANCE

 Dorsal laminectomy, annulectomy and distraction stabilization is a complex procedure which can significantly increase foraminal width, reduce pain and improve gait characteristics in dogs in the short- to long-term, and should be performed by surgeons experienced in lumbosacral pin placement.

Diagnostic Imaging in Intervertebral Disc Disease

Imaging is integral in the diagnosis of canine intervertebral disc disease (IVDD) and in differentiating subtypes of intervertebral disc herniation (IVDH). These include intervertebral disc extrusion (IVDE), intervertebral disc protrusion (IVDP) and more recently recognized forms such as acute non-compressive nucleus pulposus extrusion (ANNPE), hydrated nucleus pulposus extrusion (HNPE), and intradural/intramedullary intervertebral disc extrusion (IIVDE). Many imaging techniques have been described in dogs with roles for survey radiographs, myelography, computed tomography (CT), and magnetic resonance imaging (MRI). Given how common IVDH is in dogs, a thorough understanding of the indications and limitations for each imaging modality to aid in diagnosis, treatment planning and prognosis is essential to successful case management. While radiographs can provide useful information, especially for identifying intervertebral disc degeneration or calcification, there are notable limitations. Myelography addresses some of the constraints of survey radiographs but has largely been supplanted by cross-sectional imaging. Computed tomography with or without myelography and MRI is currently utilized most widely and have become the focus of most contemporary studies on this subject. Novel advanced imaging applications are being explored in dogs but are not yet routinely performed in clinical patients. The following review will provide a comprehensive overview on common imaging modalities reported to aid in the diagnosis of IVDH including IVDE, IVDP, ANNPE, HNPE, and IIVDE. The review focuses primarily on canine IVDH due to its frequency and vast literature as opposed to feline IVDH.

Classification of Intervertebral Disc Disease

Intervertebral disc disease (IVDD) has been recognized in dogs since the 1800s, when the first descriptions of extruded disc material within the vertebral canal were published. In the intervening time our understanding of intervertebral disc pathology in dogs and cats has increased dramatically, with many variations of IVDD described. Whilst the volume of literature and collective understanding of IVDD has expanded, there has also been scope for confusion as the definition of intervertebral disc disease, with its myriad different manifestations, becomes more complicated. A large volume of literature has aimed to combine the use of histopathology, diagnostic imaging and clinical findings to better understand the various ways in which IVDD can be classified. Much of this research has focused on the classification of mechanisms of intervertebral disc degeneration, centering around the differences between, and overlaps in, IVDD in chondrodystrophic and non-chondrodystrophic dog breeds. However, with the increasing availability of advanced imaging modalities allowing more accurate antemortem diagnosis, the concept of IVDD has expanded to include other clinical presentations that may not fit into traditional models of classification of IVDD. This review aims to provide an up to date overview of both historical and current systems of IVDD classification, highlighting the important findings and controversies underpinning them.

Comparison of medical and surgical treatment for acute cervical compressive hydrated nucleus pulposus extrusion in dogs

Although successful outcomes have been reported after medical and surgical treatment for dogs with cervical hydrated nucleus pulposus extrusion (HNPE), it is unknown which treatment option is preferred. Thirty-four dogs treated medically (n=18) or surgically (n=16) for cervical HNPE were retrospectively identified. Signalment, clinical presentation and imaging findings were compared between medically and surgically treated dogs. Medical management consisted of restricted exercise in combination with physiotherapy. Surgical treatment consisted of a ventral slot procedure. Short-term follow-up information was retrieved from re-examination visits. Long-term outcome was obtained via telephone interviews. More dogs in the surgical group demonstrated cervical hyperaesthesia on initial clinical presentation (P=0.045), otherwise there was no significant difference in signalment, clinical presentation or imaging findings between both groups. Two dogs in the medically managed group underwent surgical decompression due to an unsatisfactory response to medical management. All cases for which long-term information was available (n=30) were neurologically normal at the time of data collection. There were no significant differences for any of the short-term or long-term outcome variables between both treatment groups. This study demonstrated successful outcomes after medical or surgical treatment and suggests that both treatment modalities can be considered for dogs with cervical HNPE.

Acute Herniation of Nondegenerate Nucleus Pulposus: Acute Noncompressive Nucleus Pulposus Extrusion and Compressive Hydrated Nucleus Pulposus Extrusion

Acute herniation of nondegenerate nucleus pulposus material is an important and relative common cause of acute spinal cord dysfunction in dogs. Two types of herniation of nondegenerate or hydrated nucleus pulposus have been recognized: acute noncompressive nucleus pulposus extrusion (ANNPE) and acute compressive hydrated nucleus pulposus extrusion (HNPE). Spinal cord contusion plays an important role in the pathophysiology of both conditions. Sustained spinal cord compression is not present in ANNPE, whereas varying degrees of compression are present in HNPE. Although affected animals often present with severe neurologic signs, good outcomes can be achieved with appropriate treatment.

Parkinson Disease: An Evolutionary Perspective

There are two central premises to this evolutionary view of Parkinson disease (PD). First, PD is a specific human disease. Second, the prevalence of PD has increased over the course of human history. Several lines of evidence may explain why PD appears to be restricted to the human species. The major manifestations of PD are the consequence of degeneration in the dopamine-synthesizing neurons of the mesostriatal neuronal pathway. It is of note the enormous expansion of the human dopamine mesencephalic neurons onto the striatum compared with other mammals. Hence, an evolutionary bottle neck was reached with the expansion of the massive nigrostriatal axonal arborization. This peculiar nigral overload may partly explain the selective fragility of the human dopaminergic mesencephalic neurotransmission and the unique presence of PD in humans. On the other hand, several facts may explain the increasing prevalence of PD over the centuries. The apparently low prevalence of PD before the twentieth century may be related to the shorter life expectancy and survival compared to present times. In addition, changes in lifestyle over the course of human history might also account for the increasing burden of PD. Our hunter-gatherers ancestors invested large energy expenditure on a daily basis, a prototypical physical way of life for which our genome remains adapted. Technological advances have led to a dramatic reduction of physical exercise. Since the brain release of neurotrophic factors (including brain-derived neurotrophic factor) is partially exercise related, the marked reduction in exercise may contribute to the increasing prevalence of PD.

Canine acute cervical myelopathy: Hydrated nucleus pulposus extrusion or intraspinal discal cysts?

OBJECTIVE

To differentiate between hydrated nucleus pulposus extrusion and ventral intraspinal discal cysts in dogs.

STUDY DESIGN

Prospective case series.

ANIMALS

Twenty dogs with acute onset of cervical myelopathy due to hydrated nucleus pulposus extrusion or ventral intraspinal discal cysts.

METHODS

Clinical and magnetic resonance (MR) imaging findings, outcome after surgical treatment, cytologic and histologic findings of compressive material were taken into account. Comparisons and considerations were done between findings reported herein and what was previously described as suspected hydrated nucleus pulposus extrusion and intraspinal cysts.

RESULTS

All dogs were presented with acute onset of cervical myelopathy. MR imaging showed compressive cervical myelopathy at C2-C3 (n = 1), C3-C4 (n = 6), C4-C5 (n = 8), and C5-C6 (n = 5) intervertebral disc spaces, due to extradural material suggestive of either partially hydrated nucleus pulposus extrusion or intraspinal discal cyst, with T2 hyperintense and T1 iso-hypointense signal and variable contrast enhancement after gadolinium injection. All dogs were treated surgically by ventral slot (n = 15) or dorsolateral hemilaminectomy (n = 5). All dogs had a favorable outcome and regained a normal gait. The extradural material collected at surgery varied from liquid to more obvious gelatinous material. Cytologic or histologic examination of the material revealed similar findings for all dogs, compatible with partially degenerated nucleus pulposus.

CONCLUSIONS

Dogs with acute onset of compressive cervical myelopathy due to extradural material resembling human intraspinal cysts on MR images are most likely to have extrusion of partially degenerated nucleus pulposus and should be treated accordingly.

Detection of compressive hydrated nucleus pulposus extrusion in dogs with multislice computed tomography

Compressive hydrated nucleus pulposus extrusion (HNPE) in dogs is defined as acute extradural compression by hydrated nucleus pulposus material at the level of the associated intervertebral disc. Magnetic resonance imaging (MRI) is the imaging modality of choice for diagnosis of HNPE. The aims of this study were to determine the usefulness of unenhanced computed tomography (CT) and contrast enhanced CT (CE-CT), and the sensitivity and specificity of CE-CT, for detection of compressive HNPE. Using CE-CT, HNPE was visualised as a hypodense extradural compressive lesion with rim enhancement immediately dorsal to the intervertebral disc space, with a sensitivity of 91% and a specificity of 100%. CE-CT is a useful technique to detect compressive HNPE in dogs. However, if no clear lesion is identified with CE-CT, or if additional information about intramedullary changes is required, MRI still needs to be performed.

Hydrated nucleus pulposus extrusion in dogs: correlation of magnetic resonance imaging and microsurgical findings

Background

Magnetic resonance imaging (MRI) patterns of canine cervical hydrated nucleus pulposus extrusion (HNPE) have been described by a few reports, but the correlation between microsurgical and MRI features has never been investigated. The aim of this study was to compare the MRI features of HNPE with microsurgical findings and cytological outcomes and also to investigate the anatomical and pathophysiological aspects of the disease.

Methods

A prospective clinical study was conducted in 36 dogs suffering from HNPE. The diagnosis was based on high-field MRI findings of ventral extradural lesions, adjacent to the dorsal aspect of intervertebral discs, characterised by high signal intensity in T2-weighted sequences and hypointensity in T1-weighted sequences. MRI images were analysed with regard to the intervertebral space involved, the grading of spinal cord compression, the signal intensity and distribution of the material, and the thickness and signal intensity of the involved discs. All patients underwent microsurgical decompression and direct observations were recorded and films of the surgical procedure analysed.

Results

The majority of patients had acute onset of clinical signs (78 %), the patient did not exhibit signs of pain in 75 % of dogs and neurological deficits varied from slight tetraparesis (33 %) to tetraplegia (28 %). The localization of the extruded disc material was ventral relative to the dorsal longitudinal ligament that was lifted dorsally and appeared intact at the site of compression. Direct microsurgical observations of the HNPE sites showed that extruded disc material was collected within the fibres of the dorsal longitudinal ligament. The consistency was gelatinous in 42 %, water-like in 33 %, and lumpy liquid in 25 % of cases. Cytological samples did not detect the presence of inflammation, bacteria, fungi, neoplastic cells or foreign material.

Conclusions

Microsurgical features of HNPE suggest that the extruded disc is collected within the fibres of the dorsal longitudinal ligament and this may explain the typical MRI appearance of this disease. Further pathophysiological studies are needed to investigate why the cervical nucleus pulposus extrusion appears to occur without obvious trauma.

Electronic supplementary material

The online version of this article (doi:10.1186/s13028-015-0151-x) contains supplementary material, which is available to authorized users.

A Review of Fibrocartilaginous Embolic Myelopathy and Different Types of Peracute Non-Compressive Intervertebral Disk Extrusions in Dogs and Cats

This review discusses terminology, pathological, clinical, and magnetic resonance imaging (MRI) findings, treatment, outcome, and prognostic factors of fibrocartilaginous embolic myelopathy (FCEM), acute non-compressive nucleus pulposus extrusion (ANNPE), and intradural/intramedullary intervertebral disk extrusion (IIVDE). FCEM, ANNPE, and IIVDE have a similar clinical presentation characterized by peracute onset of neurological dysfunction that is generally non-progressive after the initial 24-48 h. Differentiating between these conditions can be challenging, however, certain clinical and imaging findings can help. FCEM can occur in both adult and immature animals, whereas ANNPE or IIVDE have been reported only in animals older than 1 year. In dogs, ANNPE and IIVDE most commonly occur in the intervertebral disk spaces between T12 and L2, whereas FCEM has not such site predilection. In cats, FCEM occurs more frequently in the cervical spinal cord than in other locations. Data on cats with ANNPE and IIVDE are limited. Optimal MRI definition and experience in neuroimaging can help identify the findings that allow differentiation between FCEM, ANNPE, and IIVDE. In animals with ANNPE and IIVDE, the affected intervertebral disk space is often narrowed and the focal area of intramedullary hyperintensity on T2-weighted images is located above the affected intervertebral disk space. In dogs with ANNPE signal changes associated with the extruded nucleus pulposus and epidural fat disruption can be identified in the epidural space dorsal to the affected intervertebral disk. Identification of a linear tract (predominantly hyperintense on T2-weighted images, iso to hypointense on T1-weighted images and hypointense on T2*-weighted gradient recall echo images) extending from the intervertebral disk into the spinal cord parenchyma is highly suggestive of IIVDE. Treatment of FCEM and ANNPE is conservative. Dogs reported with IIVDE have been managed either conservatively or surgically. Prognostic factors include degree of neurological dysfunction (particularly loss of nociception) and disease-specific MRI variables.

Discal cysts of the cervical spine in two dogs

Discal cysts, which lie directly over intervertebral discs, are rare. Two old dogs with tetraparesis were referred to our facility. In both animals, magnetic resonance imaging revealed intraspinal extradural cystic mass lesions that were dorsal to degenerative intervertebral discs at the C3-C4 level. These lesions had low signal intensity on T1-weighted images, and high signal intensity on T2-weighted images. A ventral slot approach was used to perform surgical decompression, after which the symptoms improved remarkably. Discal cysts should be included in the differential diagnosis of dogs with cervical pain and tetraparesis. One effective treatment for discal cysts is surgical intervention.

Hydrated nucleus pulposus herniation in seven dogs

The clinical signs, magnetic resonance imaging (MRI) findings, treatment and follow-up in seven dogs with hydrated nucleus pulposus extrusion (HNPE) are reported. All dogs had tetraparesis or tetraplegia. T2-weighted MRI revealed extradural hyperintense homogeneous material compressing the cervical spinal cord. After conservative treatment (five dogs) or surgical decompression (two dogs), all dogs returned to ambulatory function within 1 month. Follow-up MRI in conservatively treated dogs revealed complete disappearance of the extruded material. Histopathological examination of surgical specimens confirmed that the retrieved material was extruded nucleus pulposus with evidence of early degeneration.